%0 Journal Article
%A Aslam, N.
%A Longo, V.
%A Keuning, W.
%A Roozeboom, F.
%A Kessels, W. M. M.
%A Waser, R.
%A Hoffmann-Eifert, S.
%T Influence of stoichiometry on the performance of MIM capacitors from plasma-assisted ALD Sr x Ti y O z films
%J Physica status solidi / A
%V 211
%N 2
%@ 1862-6300
%C Weinheim
%I Wiley-VCH
%M FZJ-2014-03495
%P 389 - 396
%D 2014
%X Strontium titanate, SrxTiyOz (STO), thin films with various cation stoichiometries were deposited by plasma-assisted atomic layer deposition (ALD) using cyclopentadienyl-based metal precursors and oxygen plasma as counter-reactant. [Sr]/([Sr] + [Ti]) compositions ranging from 0.46 to 0.57 were obtained by changing the (SrO)/(TiO2) ALD cycle ratios. As-deposited 15–30 nm thick SrxTiyOz films prepared at 350 °C on Pt-coated silicon substrates were amorphous. Post-annealing at 600/650 °C for 10 min under N2 gas resulted in a crystallization into the perovskite phase. Stoichiometric STO and Sr-rich STO films exhibited a certain degree of (111) texture while the Ti-rich STO films showed a lower degree of crystallization. Crystallized layers exhibited a smaller band gap Eg than amorphous ones, while within the stoichiometry series the value of Eg increased with increasing Sr-content. Within the stoichiometry series Pt/STO/Pt structures with Sr-rich STO films showed the lowest leakage current densities. At 1.0 V values of about 2 × 10−8 and 5 × 10−6 A cm−2 were obtained for the as-deposited and the annealed films, respectively. Highest capacitance density was obtained for 15 nm polycrystalline stoichiometric SrTiO3 films resulting in a capacitor equivalent thickness CET of about 0.7 nm. Pt/SrxTiyOz/Pt capacitors with the STO being in amorphous state exhibited a positive voltage nonlinearity factor α of about 400 ppm V−2, while the negative α-values for crystallized films showed a systematic variation with the stoichiometry, the degree of crystallization and the thickness of the STO layer. This demonstrates that a broad performance range of MIM capacitors is accessible by controlling the stoichiometry and the degree of crystallization of plasma-assisted ALD SrxTiyOz thin films.
%F PUB:(DE-HGF)16
%9 Journal Article
%U <Go to ISI:>//WOS:000332000500020
%R 10.1002/pssa.201330101
%U https://juser.fz-juelich.de/record/154093